1. Technical Field
The present invention relates to differential adjusters, and, in particular, to a miniaturized differential adjustment apparatus that allows for minute, precise adjustments, for example, of optical components mounted in an adjustable mechanical mount used for precision alignment.
2. Discussion of Related Art
Investigations of optical phenomena and testing of optical systems often require increasingly precise orientations of optical elements such as mirrors, lenses, filters, optical fibers, and other optical elements. Research into optical transmission of data, for example, requires precisely oriented components to manipulate light of various wavelengths into and out of optical wave-guides, which may have core sizes of less than about 0.010 mm. In research environments, various components, for example mirrors, filters and/or lenses, can be mounted on an optical mount for use on an optics table. Considerable effort is often expended in obtaining a proper optical adjustment of the optical components to facilitate the desired optical alignment. As optics technology evolves, the number of optical elements per unit volume grows, and the tolerances on the alignment of the individual optical components becomes smaller, hence requiring more precise alignment devices that occupy smaller volumes.
Highly accurate positional adjustments are also utilized in other areas, for example the micro-manipulation of biological samples. High positioning accuracy can facilitate precise positioning of samples being viewed under high magnification, or the positioning of various probes. Similar high precision requirements are also found in semiconductor manufacturing because as the feature size of the integrated circuits shrinks, the need for micro-positioning tools grows.
Adjustment of these various components can often be accomplished with screw-based adjusters. These adjusters may be mounted on holders for the respective component to be adjusted or may be utilized in translation-type mounts, typically referred to as XYZ translation stages. Within the optical sciences, which is typical of other fields as well, the holders are then attached to, or are a part of, larger systems or optical assemblies. Very fine and/or precise adjustments often utilize differential adjusters, which utilize two different threads arranged such that the net linear movement affected is a result of the difference in the pitch of the two different threads.
However, typical differential adjuster designs in the market are too large and bulky to be of practical use in miniature mechanical devices such as mirror mounts or fiber optic alignment systems. The relatively large mass and long lever arm of the typical differential adjuster, when mounted in a relatively small mechanical device such as a mirror mount, introduce significant problems in addition to just the simple problem of occupying too much space. For example, when a user touches the adjuster, its long length provides a lever arm that introduces a torque that disturbs the mount, which in turn disturbs the alignment of the mirror, causing the reflected light field reflected off the mirror to move erratically. This erratic motion inhibits the ability of the user to take full advantage of the high sensitivity of the adjuster/mount combination. In some cases, such erratic movement of the beam may result in a hazardous environment, potentially causing damage to equipment and injury to personnel.
In the past the erratic motion resulting from handling of the adjuster has been overcome by utilizing large steel mounts to provide the necessary rigidity. Opto-Sigma of Santa Ana, Calif., for example, offers a 1″ mirror mount with differential adjusters, model number 1125591, that weighs approximately 0.29 kg. Melles Griot of Carlsbad, Calif. offers a 1″ mirror mount with differential adjusters, model number 07-MAD-001, that weighs approximately 0.29 kg. Typically a 1″ mirror would not be used when building a miniaturized optical system, however, because differential adjusters have in the past been so large as to make it impractical to use them on mirror mounts that are designed for smaller optics, suppliers for smaller mirror mounts that are offered with differential adjusters have not been located.
In addition, differential adjusters in the art may include, and are controlled by, two knobs, one used to adjust the coarse portion of the adjuster and one to adjust the fine portion of the adjuster. Incorporating multiple knobs into the differential adjuster increases the bulk and size of the overall adjuster, and further exacerbates the problems discussed above. In some systems, mounts utilizing adjusters have been bulky and heavy in order to offset the deficiencies in the adjuster. This solution results in bulky and heavy mounts that are difficult to arrange in high density optical systems.
Therefore, there is a need for small differential adjusters that can accommodate precise alignment of optical components without themselves becoming a source of difficulty for alignment.